*{
  padding: 0;
  margin: 0;
}
button,input{
  outline: none;
  border: 0;
  padding: 5px 15px;
  font-size: 22px;
  margin: 10px;
}
.result{
  font-size: 32px;
  margin-left: 20px;
  margin-top: 20px;
}
.btn-group button.current{
  background-color: coral;
  color: #fff;
}
.input-group input{
  display: block;
  border-bottom: 1px solid gray;
}